This invention relates to a pneumatic power tool having an air driven rotation motor supported in a portable housing and an air inlet passage in the housing.
In particular, the invention concerns a pneumatic power tool having a speed governor for controlling the air flow through the inlet passage, and an overspeed safety device arranged in series with and upstream of the speed governor. The overspeed safety device comprises a speed responsive actuator connected to the motor and a valve means shiftable by the actuator from a normally open condition to a closed condition at motor speeds above the speed range normally covered by the speed governor.
The usual way of accomplishing the air inlet passage in the housing of the above type of tool is to have it formed integrally with the housing itself. This means that when the housing is casted the air passage is obtained by inserting cores in the casting mould. Due to the fact that it is rather difficult and time consuming to have these cores correctly located in the mould, the manufacturing cost for this type of tool housing is quite high.
Another drawback concerned with previous tools of this type is that the housing design comprising moulded-in air passages is rather bulky and heavy. These are of course undesirable characteristics of a portable power tool.
An example of such a tool is described in U.S. Pat. No 3,923,429. From the drawing figures of this patent it is evident that the moulded tool housing is quite complicated, and, in order to get access to the speed governor and overspeed safety device, the housing is built up of an assembly of separate sections.
The object of the present invention is to accomplish a pneumatic power tool of the above related type in which a new type of housing contributes to reduce the outer dimensions and weight as well as the manufacturing cost of the tool.
Further objects and advantages of the invention will be apparent from the following description: